MicroRNAs (miRNA) are small non-coding RNAs that negatively regulate post-transcriptional gene expression. Almost all human cancers are characterized by abnormal microRNA expression patterns, which are unique to tumor types. A large body of experimental evidence documents the role of miRNAs in cancer pathogenesis, and specific miRNAs function as oncogenes or tumor suppressors. Due to unique expression profiles and anti/pro-tumorigenic properties of miRNAs, efforts are underway to explore their therapeutic and diagnostic potential. Many miRNA profiling methods have been developed, ranging from Northern blotting and qRT-PCR to the more recent microarray and RNA-Seq platforms. The following chapter details an imaging technique for cellular-specific miRNA expression profiling called in situ hybridization (ISH).